12.3 supportive cells (neuroglia)

neuroglia (glial cells)

support, protect, and help neurons

oligodendrocytes

form myelin in the CNS

ependymal cells

produce and circulate cerebrospinal fluid (CSF)

(CSF - a clear, watery fluid that surrounds and cushions the brain and spinal cord, protecting them from injury) 

microglia 

immune cells that clean up debris 

astrocytes

most abundant; help form the blood-brain barrier, support neurons, regulate chemicals

perivascular feet

the expanded end-feet of astrocytes that form a sheath around the capillaries in the brain

blood-brain barrier 

protects the brain by controlling what enters from blood 

astrocytosis/sclerosis

scar tissue formed by astrocytes

schwann cells (neurolemmocytes) 

form myelin in PNS and help repair nerves 

satellite cells

adult stem cells found in skeletal muscle that are crucial for muscle growth, maintenance, and repair

gliomas 

tumor of glial cells 

myelin sheath

fatty insulation around axons that speeds signals

myelination

processes of making myelin

neurilemma 

outer layer of schwann cell around an axon 

basal lamina

thin outer covering of schwann cell

node of ranvier

gap between myelin segments

internodal segments 

myelinated regions 

initial segment

axon area right after hillock 

trigger zone

hillock + initial segment where APs begin

multiple sclerosis (MS)

immune system destroys CNS myelin

tay-sachs disease 

fatal disorder with buildup of lipids in myelin 

gangliosides

lipids that build up in tay-sachs

unmyelinated fibers 

nerve fibers without myelin; slower conduction 

regeneration tube

pathway formed by schwann cells that guides regrowing axons